1. Field of the Invention
The present application relates generally to computer systems and software. More particularly, the present application relates to query optimization for computer database systems and software.
2. Description of the Background Art
Structured Query Language (SQL) is a popular standard for querying relational database management systems (DBMS). In SQL, a user or program generates a query that specifies the data to be retrieved.
A query optimizer has the purpose of determining an optimal or near optimal plan for executing an SQL query by modeling the execution cost for each of many alternate plans. The modeling generally uses aggregate statistics about the database tables, columns and indices. The plan with the lowest estimated cost may then be chosen as the one to be used for the actual execution of the query.